Laboratory liquid handling systems are used to transport and operate on volumes of liquid. For example, one or more liquid samples may be provided in containers (e.g., microwell plates or vials) in a liquid handling system. The liquid handling system may include one or more pipettors that are used to remove (e.g., by aspirating) portions of the samples from the containers and/or to add (e.g., by dispensing) material to the samples in the containers. In some cases, it may be desirable or necessary to move labware or tools within the system. For example, it may be desired to place a lid on a container, to remove a lid from a container, or to move a container (e.g., to a heating station, agitator or sensor). It may be desirable or necessary to execute the aforedescribed procedures robotically and, in some cases, automatically and programmatically.